Broken aircraft race engines

[PWR4360-59B]

I think it would be interesting to hear about racing aircraft engine failures, fixes and special modifications. The inline engines that were used in boat racing had lots of problems, some of the fixes made it into aircraft engines, and many did not. I don't think you'd want to be welding weights on an aircraft crankshaft. Lets hear some stories.

 

[GregP]

The real issue is balance. If you balance the crankshaft, rod, and pistons, the engine should live quite well, even at WER power.

At Yancey's Allison, we balance the connecting rods within a gram, balance the pistons within a gram, and balance the crankshaft, so the engine basically runs like a turbine. Of course the owner needs to balance the prop and spinner to equal tolerances or it will still vibrate. We have no control over that, but our customers have a great experience with our engines since we take the time and effort to make them run smoothly.

It takes some work to make it right.

 

[GregP]

OK. Most of the boat guys were parts changers. There were VERY few actual mechanics. They'd assemble the engines with whatever parts they had, and never balanced or checked clearances. A lot of the boat guys would take off things that they felt were "unimportant" in a boat. Most of the time they were very wrong, sometimes wildly wrong. Their engines rarely stayed together for long due to very poor assembly techniques.

One huge mistake they made with Allisons was trying to run the PD-12K8 carburetor. It simply didn't like the pounding a boat takes and would not run well at all, usually burning pistons and / or exploding the engine. The PD-12K7 was a MUCH better boat carb, tolerated the pounding well, and would hold a tune for an entire season without trouble.

Also, they assumed a new carb in a box was good. Not true. The carbs need to be overhauled every 3 – 5 years whether in use or not, especially with attention to the diaphragm. If you don't, the carbs can spring leaks and start fires. By the time the fire guys get there, the boat had burned up and disappeared, sometimes with the driver in the pyre. If you can't afford to overhaul the carbs, don't run the big aviation V-12's.

There was post somewhere awhile back where someone said the Allisons were dropped from drag racing because they could not accelerate well, but could taxi at 150 mph! That poster was dead wrong. The Allisons were beating the fuelers in head-to-head drag racing and the NHRA banned aero engines because they could not beat the Allison. Aero engines are STILL banned in the NHRA! They were scared of the Allisons and lost to them on a very regular basis ... like every time the Allison car didn't break. As it happens, our shop did the Allison overhaul when John Rolley restored Art Arfons' Green Monster #5, and it was just here in So Cal for the Bakersfield Cacklefest and vintage dragster meet last weekend. Ran great!

Back to boats … The boat guys also tried to mount the Allisons and Merlins on wood rails that were too small for the weight and pounding. The Allison and Merlin both weighed about 1400 – 1500 pounds, depending on model, and a 10g hit in the water sometimes broke the engine mounting rails and the driver wound up wearing the Allison or Merlin in his lap.

Some years back they decided to film a movie about unlimited boats. If I recall right, it was a story about Miss Madison. Joe Yancey built the Allisons for that movie and they assembled about 10 – 12 old unlimited boats for the movie. When they were filming the movie, they hired some of the actual old drivers from the boat's previous lives. They were astounded that Joe engines ran faster than when they were racing, and did so with 100% reliability. When they asked Joe what trick he used to make that happen, he responded, "RTFB." When they asked what it stood for, he said, "read the f____ book!" All he did was to assemble the Allisons to factory tolerances, factory clearances, and he used all the factory parts. Unsurprisingly to many of us, the Allisons ran very well and very fast. Some of these old boats are still running on Joe's original overhaul all those years ago! Most of them still running get the carbs overhauled as they were instructed.

If anyone out there wants to restore an old PT boat from WWII, Joe has three old PT boat engines ready for overhaul. It would be great to hear one again, huh? Last time I hear one was when they were filming McHale's Navy!

 

[dairwin]

GregP - email sent.

Thx,

DAI

 

[PWR4360-59B]

As a youngster when I wanted to be there wrenching on those inlines in the boats, I kinda guessed it was part that RTFB deal, that caused most of the problems.
Agree there is a huge difference between a bolt twister and someone that really knows whats going on. Mounting on wood, wow no wonder all those problems back then. I can imagine the twisting and stress of that set up.

 

[GregP]

Dairwin, no email received! Don't know why. Please PM instead! Thanks!

 

[dairwin]

GregP - PM sent!

Thx,

DAI

 

[tyrodtom]

As a youngster when I wanted to be there wrenching on those inlines in the boats, I kinda guessed it was part that RTFB deal, that caused most of the problems.
Agree there is a huge difference between a bolt twister and someone that really knows whats going on. Mounting on wood, wow no wonder all those problems back then. I can imagine the twisting and stress of that set up.

It's not that it was mounted on wood that was the problem, it's HOW it was mounted on wood. If you've got a wood boat, or airplane, at some point you have to mount the engine, or the engine mount on wood.

 

[GregP]

Wood is the original compisite material. Very strong and resiliant.

The problem was undersestimating the weight and stresses the unlimited hydroplanes encountered. In other words, poor design. Many of the unlimiteds were cobbled together by people who had no design experience and were NOT engineers or designers. They discovered their mistakes rather violently.